The purpose of this Core is to provide molecular biological and FIV-related cell culture support for he overall program. The Core will prepare, over-express, purify, and test all proteases to be employed in studies by the investigators of the Program Project. Constructs will include wild type ind drug-resistant proteases from HIV-1 and FIV, as well as a discrete set of tethered dimers that ire hybrids between wild type and drug-resistant proteases. The constructs will be prepared in E. :oh and re-folded by procedures well established in our laboratory. Construct proteases will be monitored for catalytic efficiency, using either fluorigenic substrates at our disposal or by HPLC analysis, where required. Bacterial, insect, and mammalian cell expression systems are also maintained to facilitate over-expression of natural substrates, where required. The Core will also test he efficacy of compounds developed by the Program for ability to inhibit FIV expression in tissue culture. Results may then be compared to efficacy against HIV-1 expression ex vivo, to be carried out by the Torbett laboratory.